1 Corinthians 1:1

Paul’s description of himself as one whom God had called to be an apostle of Jesus Christ reminded his original readers of his privilege and authority (cf. Romans 1:1). The idea of authority received added strength from the reference to the will of God (cf. 2 Corinthians 1:1; Ephesians 1:1; Colossians 1:1; 2 Timothy 1:1).

Sosthenes was probably the same Sosthenes who was the ruler of the synagogue in Corinth (Acts 18:17). He was with Paul in Ephesus when Paul penned this epistle. Though Luke did not record his conversion in the Book of Acts, Sosthenes quite clearly became a believer, assuming this was the same man. Probably he was the same man, and Paul referred to him because the Corinthians knew him well.